1. Field of the Invention
The present invention relates to a steering apparatus.
2. Description of Related Art
In a saddle-type vehicle such as an all terrain vehicle (ATV), a steering apparatus (particularly, a motor-driven power steering apparatus) is installed between a steering shaft of handlebars and a steering member of wheels (front wheels). The motor-driven power steering apparatus is an apparatus that supplements a steering force applied by a driver on the handlebars with an assist torque that is generated from an electric motor.
The motor-driven power steering apparatus has built-in members such as an input shaft, a torsion bar, and an output shaft. The input shaft is connected to the steering shaft of the handlebars. The torsion bar connects the input shaft and the output shaft. A steering arm is attached to the output shaft (for example, refer to JP-A-2007-196927) (FIG. 2).
The steering arm is a steering member of the wheels (front wheels). The steering arm is configured to turn about the output shaft. The steering arm is provided with tie rod holes to which tie rods are respectively attached. The wheels are respectively connected to the tie rods.
When the driver turns the handlebars to the maximum steering angle or greater in a clockwise direction or a counter-clockwise direction, the motor-driven power steering apparatus is required to restrict the turning of the handlebars in such a manner that a vehicle does not roll over in a lateral direction. While the vehicle is traveling on a rough road, even without the driver's turning of the handlebars, an external force originating from a protrusion (convex portion) or the like on a road surface may be input to the motor-driven power steering apparatus and the handlebars via the wheels (front wheels), and thereby this may turn the handlebars to the maximum steering angle or greater. Even in this case, the motor-driven power steering apparatus is required to restrict the turning of the handlebars in such a manner that the vehicle does not roll over in the lateral direction. The motor-driven power steering apparatus is provided with an arm stopper mechanism for such a function which restricts the turning angle of the steering arm via a stopper.
The stopper is provided to protrude downward from a lower surface of a housing of the motor-driven power steering apparatus. When the driver turns the handlebars to the maximum steering angle or greater in the clockwise direction or the counter-clockwise direction, or when the handlebars turn to the maximum steering angle or greater due to an external force that is input via the wheels (front wheels), a striking surface of the steering arm strikes against a contact surface of the stopper. Accordingly, the turning angle of the steering arm is restricted by the arm stopper mechanism via the stopper, and thereby the turning of the handlebars is restricted.
In this motor-driven power steering apparatus, when a bending load applied to the output shaft increases, an excessive load may be applied to a bearing that supports the output shaft, or to a housing in the vicinity of the bearing. Accordingly, in the motor-driven power steering apparatus, a bending load is preferably prevented from being applied to the output shaft.